Yuu is a demon hunter that uses the fake name “Tsubasa” to deal with clients, he also treats it as a sort of last name. He spends his days killing demons for people in exchange for money and possess a powerful sword that draws its energy from shadows and the darkness.

He tends to be rather aloof but with a cocky streak, and usually tries to emotionally detach himself from people because he doesn't want to involve them in his world. This changes when he meets and takes Toris in as his apprentice; though he tells himself that it's simply because it will make his demon hunting job easier. He becomes rather fond of Toris and grows quite protective of him; always ready to defend the younger boy from demon attacks.

His hair and eyes have changed colour to silver due to training his body to use magic, a side effect of a human whose magic levels have become higher than the average person. Their hair usually turns silver or white with the eyes being silver or gold.

He is the childhood friend of Cecil, who he also has a romantic interest in. He is repeatedly frustrated by Cecil's denial of his feelings due his work as a priest and though he loves his friend dearly sometimes he just wants to hit him for being so stubborn. Never the less he respects Cecil's chosen path as a Demon Exorcist being full aware his friend would be far too kind to be an actual Demon Hunter. He worries about his trusting nature still and isn't aware that Cecil can actually be rather terrifying when angered.